Hepatitis A is a viral infection of the liver caused by hepatitis
A virus (HAV). The clinical manifestations of HAV infection range
in clinical severity from no symptoms to a mild illness lasting
1–2 weeks to a severely disabling disease lasting several
months. Clinical manifestations of hepatitis A often include fever,
malaise, anorexia, nausea, and abdominal discomfort, followed
within a few days by jaundice.

HAV is shed in the feces of persons with HAV infection. Transmission
can occur through direct person-to-person contact; through exposure
to contaminated water, ice, or shellfish harvested from sewage-contaminated
water; or from fruits, vegetables, or other foods that are eaten
uncooked and that were contaminated during harvesting or subsequent
handling.

HAV infection is common (high or intermediate endemicity) throughout
the developing world, where infections most frequently are acquired
during early childhood and usually are asymptomatic or mild. In
developed countries, HAV infection is less common (low endemicity),
but communitywide outbreaks still occur in some areas of the United
States.

Risk for Travelers

The risk of acquiring HAV infection for U.S. residents traveling
abroad varies with living conditions, length of stay, and the
incidence of HAV infection in the area visited. Travelers to North
America (except Mexico), Japan, Australia, New Zealand, and developed
countries in Europe are at no greater risk for infection than
in the United States. For travelers to low-income countries, risk
for infection increases with duration of travel and is highest
for those who live in or visit rural areas, trek in back country
areas, or frequently eat or drink in settings of poor sanitation.
Nevertheless, many cases of travel-related hepatitis A occur in
travelers to developing countries with “standard”
tourist itineraries, accommodations, and food consumption behaviors.

Clinical Presentation

The incubation period for hepatitis A averages 28 days (range
15–50 days). Hepatitis A typically has an abrupt onset of
symptoms that can include fever, malaise, anorexia, nausea, abdominal
discomfort, dark urine, and jaundice. The likelihood of having
symptoms with HAV infection is related to the infected person's
age. In children <6 years old, most (70%) infections are asymptomatic;
if illness does occur it is not usually last <2 months. There
is no chronic or long-term infection associated with hepatitis
A, but 10% of infected persons will have prolonged or relapsing
symptoms over a 6- to 9-month period. The overall case-fatality
rate among cases reported to CDC is 0.3%; however, the rate is
1.8% among adults >50 years of age.

Prevention

Hepatitis A is one of the most common vaccine-preventable diseases
in travelers. Hepatitis A vaccine, immune globulin (IG), or both,
are recommended for all susceptible persons traveling to or working
in countries with an intermediate or high endemicity of HAV infection.

For maximum protection, Hepatitis A vaccination should be given
4-weeks before first travel to countries with high or intermediate
endemicity. One month after receiving the first dose of monovalent
hepatitis A vaccine, 94%–100% of adults and children will
have protective concentrations of antibody. The final dose in
the hepatitis A vaccine series is necessary to promote long-term
protection. Many persons will have a detectable antibody to hepatitis
A virus (anti-HAV) response to the monovalent vaccine by 2 weeks
after the first vaccine dose.